1. Field of the Invention
The present invention relates to an inductive type thin film magnetic head used for a floating type magnetic head or the like, and more particularly, to a thin film magnetic head which can reduce eddy current loss without forming a secondary magnetic gap by improving the structure of a core layer, and a method of fabricating such a thin film magnetic head.
2. Description of the Related Art
FIG. 7 is a longitudinal sectional view of a conventional thin film magnetic head.
The thin film magnetic head shown in FIG. 7 is a so-called xe2x80x9ccombined magnetic headxe2x80x9d, in which a reading head, using a magnetoresistance effect, and an inductive magnetic head, for writing the signal into a recording medium such as a hard disk, are deposited. The combined magnetic head is provided on the end of a slider of a floating type magnetic head on the trailing side facing a recording medium such as a hard disk.
As shown in FIG. 7, an underlying layer 41, a lower shield layer 42, a lower insulating layer 43, a magnetoresistive element layer 44, and an upper insulating layer 45 are sequentially deposited on a substrate 40 composed of Al2O3xe2x80x94TiC, and an inductive magnetic head for writing is formed thereon.
A lower core layer 20 is composed of a magnetic material having high magnetic permeability such as an Fe-Ni alloy (permalloy). In a combined magnetic head in which the inductive magnetic head shown in FIG. 7 is sequentially deposited on a reading head using a magnetoresistance effect, the lower core layer 20 functions also as an upper shield layer for the reading head.
A gap layer 2 composed of a nonmagnetic material such as Al2O3 (aluminum oxide) is formed on the lower core layer 20. An insulating layer 3 composed of a resist or other organic resin is formed on the gap layer 2.
A coil layer 4, composed of a conductive material having low electrical resistance such as Cu, is spirally formed on the insulating layer 3. Although the coil layer 4 is formed so as to go around a base 21b of an upper core layer 21, only a portion of the coil layer 4 is shown in FIG. 7.
An insulating layer 5 composed of a resist or other organic resin is formed on the coil layer 4. The upper core layer 21 is formed by plating a magnetic material such as a permalloy on the insulating layer 5. A tip 21a of the upper core layer 21 is joined to the lower core layer 20 with the gap layer 2 therebetween at the section facing a recording medium to form a magnetic gap having a gap length Gl1. Also, a gap depth Gd is determined by the depth of the tip 21a.
Also, the base 21b of the upper core layer 21 is connected to the lower core layer 20 through a hole formed in the gap layer 2 and the insulating layer 3.
In the inductive magnetic head for writing, when a recording current is applied to the coil layer 4, a recording magnetic field is induced to the lower core layer 20 and upper core layer 21, and a magnetic signal is recorded onto a recording medium such as a hard disk by means of a leakage magnetic field from the magnetic gap between the lower core layer 20 and the tip 21a of the upper core layer 21.
Although the recording frequency must be increased in order to meet the high-density recording, if the resistivity in the lower core layer 20 and the upper core layer 21 is low, eddy-current heat loss increases at high frequencies.
Therefore, the resistivity in the lower core layer 20 and the upper core layer 21 must be increased, and one of the known methods for increasing the resistivity is to change the structure of the lower and upper core layers 20 and 21 from a single layer to a laminate.
In accordance with Japanese Patent Laid-Open Nos. 63-244407 and 1-102712, as shown in FIG. 8, an upper core layer 21 (and/or a lower core layer 20) is formed of a laminate in which a nonmagnetic material layer 24 is interposed between magnetic material layers 22 and 23.
In such a laminate, eddy current loss can be reduced.
However, as shown in FIG. 8, the nonmagnetic material layer 24 is revealed to the surface (air bearing surface) facing a recording medium D, and magnetic gaps (secondary magnetic gaps) having a gap length Gl2 are formed by nonmagnetic material layers 24.
Accordingly, in the thin film magnetic head shown in FIG. 8, in addition to a magnetic gap having a gap length Gl1 by a gap layer 2, the magnetic gaps by the nonmagnetic material layer 24 (hereinafter referred to as xe2x80x9csecondary magnetic gapsxe2x80x9d) are formed, resulting in unstable recording characteristics.
In particular, if a secondary magnetic gap is formed on the upper core layer 21, the secondary magnetic gap is located on the trailing side in relation to the original magnetic gap toward the recording medium D, and since the secondary magnetic gap is scanned after the original magnetic gap is scanned toward the recording medium D, the leakage magnetic field from the secondary magnetic gap largely affects the recording medium D.
Japanese Patent Laid-Open No. 63-247906 discloses a thin film magnetic head in which the structure of the tip of a core layer has been improved so as not to form a secondary magnetic gap in the core layer.
In the thin film magnetic head disclosed in the patent described above, as shown in FIG. 9, a nonmagnetic material layer 24 is formed in regions other than a region near a tip 21a of an upper core layer 21, and the nonmagnetic material layer 24 is not exposed at the surface facing a recording medium D.
By employing such a structure, no trouble is caused by secondary magnetic gaps, and because of the laminate in the regions other than the tip 211, there is low eddy-current heat loss, enabling an improvement in recording characteristics at high frequencies.
However, since the nonmagnetic material layer 24 is not formed near the tip 21a of the upper core layer 21, the region near the tip 21a is single-layered, which increases eddy current loss near the tip 21a. Also, the fabrication process becomes significantly complex.
The present invention has been achieved in order to overcome the difficulties noted above with respect to the conventional art. It is an object of the present invention to provide a thin film magnetic head that does not cause a secondary magnetic gap and that can reduce eddy current loss by forming a core layer into a laminate having a-nonmagnetic material layer interposed between magnetic material layers, and, in particular, by improving the structure of the tip of the core layer.
In accordance with the present invention, a thin film magnetic head includes first and second core layers composed of a magnetic material, and a coil layer provided between the core layers for inducing a recording magnetic field to both core layers. At least one of the core layers is a laminate in which a nonmagnetic material layer is interposed between magnetic material layers, the nonmagnetic material layer is exposed between the first and second core layers at the surface facing a recording medium, and a magnetic gap is formed by the nonmagnetic material layer.
Preferably, a core layer on the trailing side is a laminate.
The nonmagnetic material layer may be formed by oxidizing a nonmagnetic metal layer.
Also, in accordance with the present invention, in a method of fabricating a thin film magnetic head, the head including first and second core layers composed of a magnetic material, a gap layer composed of a nonmagnetic material provided between the core layers, a coil layer for inducing a recording magnetic field to both core layers and an insulating layer for covering the coil layer, the method includes the steps of:
after forming the gap layer on the lower core layer and forming the coil layer and the insulating layer on the gap layer, forming a magnetic underlying layer to extend from the gap layer to the insulating layer;
forming a first magnetic material layer on the underlying layer excluding a tip region that includes a magnetic gap formation section;
removing the underlying layer in the tip region, and forming a nonmagnetic material layer to extend from the gap layer in the tip region without the underlying layer to the first magnetic material layer; and
forming an underlying layer composed of a magnetic material on the nonmagnetic material layer, and further forming a second magnetic material layer on the underlying layer.
In accordance with the present invention, after forming the first magnetic material layer, a nonmagnetic metal layer may be formed to extend from the gap layer in the tip region to the first magnetic material layer, and a nonmagnetic material layer may be formed by anodizing the nonmagnetic metal layer.
Also, a magnetic gap may be formed by interposing the nonmagnetic material layer between the first magnetic-material layer and the second magnetic material layer in the tip region, instead of forming the gap layer between the lower core layer and the upper core layer.
In accordance with the present invention, the core layer takes the form of a laminate including the nonmagnetic material layer interposed between the first and second magnetic material layers, and thus no secondary magnetic gap is formed, enabling a reduction in eddy current loss.
As illustrated in FIGS. 1 to 4, an upper core layer 6 in the present invention takes the form of a laminate including a first magnetic material layer 7, a nonmagnetic material layer 8, and a second magnetic material layer 9, however, the first magnetic material layer 7 is not formed in the tip region, and the upper core layer 6 in the tip region is formed of the nonmagnetic material layer 8 and the second magnetic material layer 9.
The nonmagnetic material layer 8 is formed in contact with a gap layer 2 and is exposed at the surface facing a recording medium D, as illustrated in FIG. 1.
A magnetic gap having a gap length Gl is formed by the gap layer 2 and the nonmagnetic material layer 8, and the nonmagnetic material layer 8 does not function as a secondary magnetic gap as has been seen in conventional art.
In comparison with the conventional single-layered upper core layer 21 (refer to FIG. 7), the first magnetic material layer 7 and the second magnetic layer 9 are formed thinly, and also, the first magnetic material layer 7 and the second magnetic material layer 9 are electrically isolated from each other by the nonmagnetic material layer 8, and thus eddy current loss can be properly reduced.
Although, in the thin film magnetic head shown in FIG. 1, the upper core layer 6 only is formed as a laminate and the lower core layer 1 is single-layered, preferably the lower core layer 1 is also formed as a laminate similarly to the upper core 6.
In such a case, as shown in FIG. 2, preferably, a nonmagnetic material layer 8 included in the lower core layer 1 is formed in contact with the gap layer 2 in the tip region in a manner similar to that of the nonmagnetic material layer 8 included in the upper core layer 6 so that a secondary magnetic gap is not formed.
However, the lower core layer 1 which corresponds to a core on the leading side may be a laminate in which the first magnetic material layer 7, the nonmagnetic material layer 8, and the second magnetic material 9 are formed in parallel, that is, the nonmagnetic material layer 8 may not be formed in contact with the gap layer 2 in the tip region, as shown in FIG. 3.
With such a structure, although a secondary magnetic gap is formed by the nonmagnetic material layer 8 in the lower core layer 1, even if the secondary magnetic gap is formed in the lower core layer 1, recording characteristics are not greatly affected by this, because of the reason described below.
Since the lower core layer 1 lies on the leading side, as shown in FIG. 3, when the recording medium D drives in the direction shown by an arrow, the recording signal is written into the recording medium D first by the magnetic gap formed in the lower core layer 1.
However, the recording signal is erased by the leakage magnetic field from the magnetic gap having the gap length Gl, which is located on the trailing side, and only the recording signal from the correct magnetic gap continues to be written into the recording medium D.
Therefore, when the lower core layer 1 on the leading side is formed as a laminate including the nonmagnetic material layer 8 provided between the first magnetic material layer 7 and the second magnetic material layer 9, even if the nonmagnetic material layer 8 is not brought into contact with the gap layer 2 at the surface facing the recording medium, recording characteristics are not greatly affected.
On the contrary, if a secondary magnetic gap is formed in the upper core layer 6 which corresponds to a core on the trailing side, the recording signal written into the recording medium D by the leakage magnetic field from the correct magnetic gap is erased by the leakage magnetic field from a secondary magnetic gap formed in the upper core layer 6, and thus recording characteristics become unstable.
Therefore, with respect to the upper core layer 6 on the trailing side, the nonmagnetic material layer 8 in the tip region must be formed in contact with the gap layer 2 so that no secondary magnetic gap is formed by the nonmagnetic material layer 8.
As described above, in accordance with the present invention, at least one of first and second core layers is formed as a laminate including a nonmagnetic material layer provided between magnetic material layers, and also, the nonmagnetic material layer is formed such that the nonmagnetic material layer is exposed between the first and second core layers at the surface facing a recording medium, and thus no secondary magnetic gap is formed, enabling a reduction in eddy current loss.